Welcome to Tips of the day! Here our some css components people asks about.
Code 1:

/* This code will effect the whole page */

*
{
/* Code here*/
}

Code 2:

/* This will place an object in center */

margin:auto;
padding:auto;

Code 3:

/* This will reset basic browser stuff */

margin:0;
padding:0;
border:0;

/* usually placed between *{ /* here */} */